In a conventional radio communication system, there are cases where signals of other systems act as interference signals on a desired signal and thereby a communication environment is deteriorated.
For example, in broadcasting satellite reception equipment and so forth having a BS (Broadcasting Satellite) antenna that is installed in each home, there are many cases where it is frequency-converted in order to process a received signal, and when a radio wave leaks out of the reception equipment on that occasion, such a case that it interferes with a band of a mobile phone system.
In a case where a band of a signal that acts as the interference signal on the band of the mobile phone system that works as a desired signal is wider than the band of the mobile phone system, it becomes difficult to remove it as the interference signal by a filter and so forth. In addition, when the interference signal is a known one, it is also possible to remove it by generating a replica as a reference. However, when the replica of the interference signal cannot be prepared, it becomes difficult to remove only the interference signal.